org.eclipse.jgit.test/tst/org/eclipse/jgit/diff/HistogramDiffTest.java

/*
 * Copyright (C) 2010, Google Inc.
 * and other copyright owners as documented in the project's IP log.
 *
 * This program and the accompanying materials are made available
 * under the terms of the Eclipse Distribution License v1.0 which
 * accompanies this distribution, is reproduced below, and is
 * available at http://www.eclipse.org/org/documents/edl-v10.php
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or
 * without modification, are permitted provided that the following
 * conditions are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials provided
 *   with the distribution.
 *
 * - Neither the name of the Eclipse Foundation, Inc. nor the
 *   names of its contributors may be used to endorse or promote
 *   products derived from this software without specific prior
 *   written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.eclipse.jgit.diff;

import static org.junit.Assert.assertEquals;

import org.junit.Test;


public class HistogramDiffTest extends AbstractDiffTestCase {
	@Override
	protected HistogramDiff algorithm() {
		HistogramDiff hd = new HistogramDiff();
		hd.setFallbackAlgorithm(null);
		return hd;
	}

	@Test
	public void testEdit_NoUniqueMiddleSide_FlipBlocks() {
		EditList r = diff(t("aRRSSz"), t("aSSRRz"));
		assertEquals(2, r.size());
		assertEquals(new Edit(1, 3, 1, 1), r.get(0)); // DELETE "RR"
		assertEquals(new Edit(5, 5, 3, 5), r.get(1)); // INSERT "RR
	}

	@Test
	public void testEdit_NoUniqueMiddleSide_Insert2() {
		EditList r = diff(t("aRSz"), t("aRRSSz"));
		assertEquals(1, r.size());
		assertEquals(new Edit(2, 2, 2, 4), r.get(0));
	}

	@Test
	public void testEdit_NoUniqueMiddleSide_FlipAndExpand() {
		EditList r = diff(t("aRSz"), t("aSSRRz"));
		assertEquals(2, r.size());
		assertEquals(new Edit(1, 2, 1, 1), r.get(0)); // DELETE "R"
		assertEquals(new Edit(3, 3, 2, 5), r.get(1)); // INSERT "SRR"
	}

	@Test
	public void testEdit_LcsContainsUnique() {
		EditList r = diff(t("nqnjrnjsnm"), t("AnqnjrnjsnjTnmZ"));
		assertEquals(new Edit(0, 0, 0, 1), r.get(0)); // INSERT "A";
		assertEquals(new Edit(9, 9, 10, 13), r.get(1)); // INSERT "jTn";
		assertEquals(new Edit(10, 10, 14, 15), r.get(2)); // INSERT "Z";
		assertEquals(3, r.size());
	}

	@Test
	public void testExceedsChainLength_DuringScanOfA() {
		HistogramDiff hd = new HistogramDiff();
		hd.setFallbackAlgorithm(null);
		hd.setMaxChainLength(3);

		SequenceComparator<RawText> cmp = new SequenceComparator<RawText>() {
			@Override
			public boolean equals(RawText a, int ai, RawText b, int bi) {
				return RawTextComparator.DEFAULT.equals(a, ai, b, bi);
			}

			@Override
			public int hash(RawText a, int ai) {
				return 1;
			}
		};

		EditList r = hd.diff(cmp, t("RabS"), t("QabT"));
		assertEquals(1, r.size());
		assertEquals(new Edit(0, 4, 0, 4), r.get(0));
	}

	@Test
	public void testExceedsChainLength_DuringScanOfB() {
		HistogramDiff hd = new HistogramDiff();
		hd.setFallbackAlgorithm(null);
		hd.setMaxChainLength(1);

		EditList r = hd.diff(RawTextComparator.DEFAULT, t("RaaS"), t("QaaT"));
		assertEquals(1, r.size());
		assertEquals(new Edit(0, 4, 0, 4), r.get(0));
	}

	@Test
	public void testFallbackToMyersDiff() {
		HistogramDiff hd = new HistogramDiff();
		hd.setMaxChainLength(4);

		RawTextComparator cmp = RawTextComparator.DEFAULT;
		RawText ac = t("bbbbb");
		RawText bc = t("AbCbDbEFbZ");
		EditList r;

		// Without fallback our results are limited due to collisions.
		hd.setFallbackAlgorithm(null);
		r = hd.diff(cmp, ac, bc);
		assertEquals(1, r.size());

		// Results go up when we add a fallback for the high collision regions.
		hd.setFallbackAlgorithm(MyersDiff.INSTANCE);
		r = hd.diff(cmp, ac, bc);
		assertEquals(5, r.size());
	}
}